`A` `=` `|x-7/4|` `+` `1``3/5`
`⇒` `A` `=` `|x-7/4|` `+` `8/5`
`\text{Ta có :}` `|x-7/4|` `≥` `0` `∀` `x`
`⇒``|x-7/4|` `+` `8/5` `≥` `8/5` `∀` `x`
`⇔` `A` `≥` `8/5` `∀` `x`
`\text{Dấu = xảy ra khi :}`
`|x-7/4|` `=` `0`
`⇔` `x` `-` `7/4` `=` `0`
`⇔` `x` `=` `7/4`
$\text{Vậy min A =}$ `8/5` $\text{⇔ x =}$ `7/4`